Rufus Sewell at the season 2 premiere of ‘The Diplomat’ in New York City on Oct. 24, 2024. Photo: Dominik Bindl/Getty

Anyone who’s watched The Diplomat has likely wondered at one point why Hal and Kate Wyler continue to stay married.

“They know each other well,” Rufus Sewell, who plays Hal Wyler opposite Keri Russell’s Kate, tells PEOPLE. “They know what they love and they hate about each other, and sometimes [what] they love are the things they hate about each other, and they hate the things they love about each other. It may be a marriage on its way out, but sometimes a marriage that seems like it may be on its way out is just in the middle of a change.”

Sewell, 57, says that The Diplomat creator Debora Cahn intended to show that “the seeds of divorce and hatred and lust and hating the way that your partner breathes is very much part of a lot of long-term relationships.”

“I’ve heard her say very recently, that the people whose relationships ultimately didn’t make it, it wasn’t because someone f—ed someone else. It was because they didn’t like the way the other person inhaled,” Sewell says.

Rufus Sewell as Hal Wyler and Keri Russell as Kate Wyler in ‘The Diplomat’ season 1.Netflix

As for the Wylers — who Sewell says use “political arguments as foreplay” — the British actor thinks, “They’re fantastic together and a pain in the ass together and it’s all part of the same thing.”

In real life, Sewell got married to actress Vivian Benitez in July. He says portraying someone in a not-so-loving marriage in The Diplomat hasn’t influenced how he views long-term relationships.

“I just tried to see things with my eyes and really try to be honest about my own descriptions of the world, and not descriptions of the world that would be given to me by the media” he says. “My experience in life tells me when I read this script that it is just beautifully accurate.”

Vivian Benitez and Rufus Sewell at the premiere of Old at Jazz at Lincoln Center on July 19, 2021 in New York City.Taylor Hill/FilmMagic

In season 2 of The Diplomat, Hal relies on Kate to help him physically as he rehabilitates after being injured in the explosion that took place at the end of season 1.

“He feels frustrated by the physical limitations and the fact that he can’t be as active and nimble, in the same way it felt for me when I was filming it,” Sewell says. “The fact that he has to ask her to help him with even the most mundane personal things — not that they have a problem with helping in that way, but he feels like it’s almost a premonition of what might be heading their way in terms of his age. And I think it freaks him out a bit.”

Hal’s physical limitations in season 2 represent a disruption to his relationship with Kate, too. “Even if it’s a pattern that you both complain about in terms of who does what, it could be quite unsettling when that changes,” Sewell says.

Despite his own setbacks, Hal continues to advocate for Kate to become the vice president of the United States.

“They worked together in the past when he was the No. 1 and she was there supporting him. I think there’s been times in the past when she might have been prepared to make sacrifices that he did not want her to make because of his belief in her potential and not [wanting] anything about their potential relationship to hinder her progress,” Sewell says. “And I think there’s difference in his belief in her and her idea of herself that has meant that he has felt he needs to be a little bit sneaky in the way that he maneuvers people and events and even her. All of those dark talents are employed with a very good heart behind them.”

Sewell admits he doesn’t know where life will take the Wylers, but he has started filming season 3 of The Diplomat in New York City. “We don’t know how long this is gonna go,” he says. “But you thought the end of season 1 was a shock? Just wait for the end of season 2! I can’t wait to get the public’s reaction.”